Physics Dept. Demonstration Manual

DS13 - Torque


To have the students experience torque.

  • DS13 custom torque bar (see Figure 1)
  • one 90 clamp
  • string loop, about 5 cm diameter
  • a 1 kg hook weight
  • a 2 kg slotted weight with a weight hanger (Secure the weight to the hanger using masking tape.)
  • pair of leather gloves


Have a (strong) student "volunteer" as the torque bar operator. Instruct the student that his/her job is to try and lift a mass off the floor by gripping and twisting (applying torque to) the cross bar. The student is strongly advised to wear the leather gloves supplied to avoid skin blisters.

Try the lift for:

  • the clamp about 30 cm from the cross bar with a 1 kg load.
  • move the clamp and load out to achieve a longer lever arm and try another lift.
  • repeat enough times until the relationship between torque and lever arm is clearly established.

The above can now be repeated with a 2 kg load.


The twisting process can be unkind to the hands. It might be better to use more than one volunteer to sort of spread the abuse out a little.